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Definition df-xr 6841
Description: Define the set of extended reals that includes plus and minus infinity. Definition 12-3.1 of [Gleason] p. 173. (Contributed by NM, 13-Oct-2005.)
Assertion
Ref Expression
df-xr * = (ℝ ∪ {+∞, -∞})

Detailed syntax breakdown of Definition df-xr
StepHypRef Expression
1 cxr 6836 . 2 class *
2 cr 6690 . . 3 class
3 cpnf 6834 . . . 4 class +∞
4 cmnf 6835 . . . 4 class -∞
53, 4cpr 3368 . . 3 class {+∞, -∞}
62, 5cun 2909 . 2 class (ℝ ∪ {+∞, -∞})
71, 6wceq 1242 1 wff * = (ℝ ∪ {+∞, -∞})
Colors of variables: wff set class
This definition is referenced by:  ressxr  6846  ltrelxr  6857  pnfxr  8442  mnfxr  8444  elxr  8446  xrex  8506
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